What is ehrlichiosis?

Ehrlichiosis is an illness caused by bacteria. It is spread by ticks. The illness causes fever, muscle aches, and other symptoms. It’s an uncommon illness that can affect people of all ages. It happens most often in the spring and summer months. This is when people have a higher risk of contact with infected ticks.

Ticks are a kind of parasite. They’re related to spiders and scorpions. They feed by attaching to an animal and sucking its blood. This makes it easy for ticks to spread disease.

What causes ehrlichiosis?

Ehrlichiosis is part of a group of diseases that spread through tick bites. Other diseases that spread through tick bites include Lyme disease, Rocky Mountain spotted fever, and anaplasmosis. The bacteria that cause ehrlichiosis commonly infect white-tailed deer and sometimes other animals in the wild. When a tick bites one of these animals, the tick becomes infected. As the animal runs through forest or underbrush, the ticks attach to leaves or grass. If a person then brushes against such a leaf or grass, the tick can become attached to the person. An infected tick can spread the bacteria to humans. When a tick bites a person, the bacteria go into the person’s bloodstream. The most common bacteria that cause ehrlichiosis are Ehrlichia chaffeensis. 

Ehrlichiosis is not contagious. You can’t get it from spending time with someone who has it. In rare cases, you may get it through a blood donation or organ transplant.

Who is at risk for ehrlichiosis?

Certain types of ticks can become infected with Ehrlichia bacteria. The most common is the lone star tick (Amblyomma americanum). You may have a higher risk for ehrlichiosis if you spend a lot of time outdoors in woody, bushy areas where these ticks are found. You may also have an increased risk if you live in an area of the country where lone star ticks are common. These ticks are most common in the southeastern, south-central, and mid-Atlantic regions of the U.S. But they are also seen in other areas.

What are the symptoms of ehrlichiosis?

Symptoms range from mild to life-threatening. They may include:

  • Fever and chills

  • Severe headache

  • Muscle aches

  • Nausea, vomiting, and diarrhea

  • Cough

  • Fatigue

  • Joint pain

  • Red eyes

  • Rash (more common in children than adults)

You may have only some of these symptoms. They may begin within 1 to 2 weeks of getting the tick bite. Some people can be infected and have no symptoms. Older adults and people with other health conditions, such as HIV, are more likely to have severe symptoms.

How is ehrlichiosis diagnosed?

Your healthcare provider will ask about your medical history and your symptoms. Tell your healthcare provider if you know you had a recent tick bite. Your healthcare provider may ask about your outdoor exposure in areas of the country where these ticks are common. You’ll also need a physical exam.

Your healthcare provider will need results from certain tests to diagnose the condition. These may include blood tests to check:

  • Indirect immunofluorescent assay (IFA). This test will confirm the diagnosis. But it takes about 21 days. A blood sample is taken the first week of symptoms. Then a second sample may be taken 2 to 4 weeks later to confirm.

  • Your white blood cells under a microscope. The bacteria may be seen inside the white blood cell.

  • Polymerase chain reaction. This test allows the healthcare provider to "multiply" parts of the bacteria, which can then be detected. This test is most sensitive the first week of the illness.

  • Antibodies. These may not become positive for 1 to 2 weeks. They are generally not helpful in diagnosing the infection while you are acutely ill.

Ehrlichiosis is often hard to diagnose. You may have only very mild symptoms that could be caused by many other diseases. Some people with ehrlichiosis may not know that a tick bit them. You may be referred to a healthcare provider who specializes in infectious disease for diagnosis.

How is ehrlichiosis treated?

Ehrlichiosis needs treatment right away.In most cases, treatment is started before the diagnosis is confirmed. This is done to help prevent severe complications.

Antibiotic medicine is the main treatment. Doxycycline is the antibiotic given most often. Ithas been shown to work against the bacteria. If you have early treatment and have only mild symptoms, you can probably take your antibiotic at home. Your fever will likely go away in a few days. Your other symptoms may not go away for a few weeks. 

If you have severe illness, your recovery may take longer. You may need to receive antibiotics through an IV (intravenous) line at the hospital. Some people with severe ehrlichiosis may need supportive care in an intensive care unit.

What are possible complications of ehrlichiosis?

In some cases, especially in those who have a weak immune system (such as from HIV or cancer), ehrlichiosis can cause serious complications. These include:

  • Brain problems, like confusion, seizures, or coma

  • Excess bleeding (hemorrhage)

  • Heart failure

  • Breathing (respiratory) failure

  • Kidney failure

  • Septic shock

These complications may need more treatments, such as fluids, breathing support, or kidney dialysis. They are more likely in older adults or in people with other health conditions. Very rarely, they may happen in healthy people with a delayed diagnosis who do not get the right treatment. In a small number of people, these complications can lead to death.

What can I do to prevent ehrlichiosis?

To help prevent ehrlichiosis:

  • Stay away from wooded and bushy areas with high grass and leaf litter. Walk in the center of trails instead.

  • Wear light-colored long pants and long-sleeved shirts, and enclosed shoes. Tuck your pants into your socks while out hiking.

  • Use tick repellents such as DEET or permethrin on exposed skin and clothing.

  • Do a full-body check for ticks after coming in from the outdoors.

  • Bathe or shower within a couple of hours after coming indoors, so you can more easily find and remove any ticks.

  • Examine gear and pets for ticks.

  • Tumble clothes in a dryer on high heat to kill any remaining ticks.

If you do find a tick attached to your skin, remove it within 24 hours. Make sure to:

  • Use a pair of tweezers to grasp the tick directly by the head or mouth parts. Do not grab the tick by its body.

  • Remove the tick by pulling it out firmly and directly outward.

  • Place the tick in alcohol to kill it.

  • Clean the bite wound with a disinfectant.

Take a photo of the tick. This can help identify the tick type if you have symptoms.

When should I call my healthcare provider?

Healthcare providers don’t advise preventive treatment with antibiotics, so you don’t need to call if you find a tick on your body. Most ticks don’t carry the bacteria that cause the disease. But if you have possible symptoms of ehrlichiosis within 1 to 2 weeks after a tick bite, call your healthcare provider right away.

Key points about ehrlichiosis

  • Ehrlichiosis is a type of bacterial infection spread through tick bites.

  • You have a higher risk of ehrlichiosis in the spring and summer in certain parts of the country.

  • You might have no symptoms, mild symptoms, or very severe symptoms from the infection.

  • Antibiotics are the key treatment for ehrlichiosis. Severe symptoms are rare if treatment begins right away. Call your healthcare provider if you have possible symptoms of ehrlichiosis within 1 to 2 weeks after a tick bite.

  • Most ticks do not carry the bacteria that cause ehrlichiosis. You have a much lower risk of the disease if you remove an infected tick within 24 hours.

Next steps

Tips to help you get the most from a visit to your healthcare provider:

  • Know the reason for your visit and what you want to happen.

  • Before your visit, write down questions you want answered.

  • Bring someone with you to help you ask questions and remember what your provider tells you.

  • At the visit, write down the name of a new diagnosis and any new medicines, treatments, or tests. Also write down any new instructions your provider gives you.

  • Know why a new medicine or treatment is prescribed and how it will help you. Also know what the side effects are and when you should report them to your provider.

  • Ask if your condition can be treated in other ways.

  • Know why a test or procedure is recommended and what the results could mean.

  • Know what to expect if you do not take the medicine or have the test or procedure.

  • If you have a follow-up appointment, write down the date, time, and purpose for that visit.

  • Know how you can contact your provider if you have questions.

Online Medical Reviewer: Barry Zingman MD
Online Medical Reviewer: L Renee Watson MSN RN
Online Medical Reviewer: Rita Sather RN
Date Last Reviewed: 4/1/2022
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